Pneumatic rock or coal drill



Oct. 6, 1959 W. RITCHIE ETAL PNEUMATIC ROCK ORQCOAL DRILL Filed Aug. 14} 1957 Inventors: /P/.7'c/// C. 6 0 762 175 By 3 Z/ vw m m P 22 3 04 4 7 9 O 0/3533. 7 u w 5 Na z z z g United States Patent PNEUMATIC ROCK 0R COAL DRILL William Ritchie and Charles Gordon Stephen, Aberdeenshire, Scotland, assignors to Chicago Pneumatic Tool Company, New York, N.Y., a corporation of New Jersey Application August 14, 1957, Serial No. 678,177

'5 Claims. (Cl. 121-40) This invention relates to pneumatic rock or coal drills of the kind in which the air supply to'the pneumatic motoris governed by a manually operable air valve and in which means are provided for projecting a spray of liquid, usually water, inrthe region of the drill bit for the purpose of reducing the dissipation of stone or coal dust into the ambient .air.

Liquid spraying devices in general, and swirl spraying devices in particular, dolnot operate satisfactorily unless the liquid is supplied to them at some substantial pressure,

. usually at about 15 pounds per square inch; and it has previously been proposed to include in the air supply line to the pneumatic motor of such drills a valve that is normally closed but is automatically opened when the pressure of liquid supplied to the drill exceeds some predetermined minimum.

The principal object 'of the presentinvention is to provide an improved construction of pneumatic rock or coal drill of the kind referred to in which manual opening-er the manually operable valve governing the supply of air to the pneumatic motor is precluded unless liquid at not less than a predetermined pressure suitable to the spraying device is available at the drill, A further object of the invention is to ensure that air under pressure cannot be supplied to the pneumatic motor of the drill until after a flow of liquid under pressure to the spraying device has been initiated.

According to the present invention a pneumatic drill of the kind referred to comprises a retractable obstructor normally so co-operating with the manually operable air valve as to preclude manual opening of the air'valve, and comprises means connected with the obstructor and responsive to the pressure of the liquid supplied to the liquid inlet of the drill to retract the obstructor when subjected to not less than a predetermined liquid pressure.

In particular, the drill may comprise a movable obstructor biased by a spring to a position in which it precludes manual opening of the air valve, a piston and cylinder combination connected with the obstructor, the piston and cylinder combination being so arranged and so connected to the liquid inlet of the drill that the pressure of liquid therein acts against and, when it exceeds a predetermined value, overcomes the bias of the spring, thus to retract the obstructor thereby permitting opening of the manually operable air valve.

In order to ensure that liquid is admitted to the spraying device of the drill before air is admitted to the pneumatic motor, so that a liquid spray shall be present when drilling actually commences, the air valve may be biased to its closed position and may be actuated by a member having a lost-motion connection with the valve and so biased that such lost-motion connection must be taken up before the opening of the air valve. A liquid controlling valve is then so connected with the member as to be opened thereby during the taking up of the lost-motion.

In a particular construction, the air valve may be a ICC mushroom or like rectilinearly actuated valve, having a stem. The actuating member maythen be a sleeve or thimble slidable relative to the stem and biased by a spring to ensure a normal clearance between an abutment on the sleeve or thimble (e.g. the closed end of the thimble) and the end of the stem. The sleeve or thimble is provided with a cam surface cooperating with the liquid controlling valve so as to open it during the taking up of the lost motion. valve may conveniently be of the mushroom type having a stem thatcooperates with the cam surface of the sleeve or thimble.

The invention, although not so restricted, is particularly applicable to percussive pneumatic drills, and, for the better understanding of the invention one manner of so applying it will now be described by way of example only with reference to the accompanying drawing, which is a part elevation and part longitudinalmedian section of a percussive rock drill, the parts germane to the invention being shown in section.

Referring to the drawing, the back-head of the .drillis furnished with a mushroom type manually operable air controlling valve 10, the stem of which is guided by a valve-guide 27 and the head of which cooperates with a resilient sealing 34. Air under pressure is supplied through a hose-nipple 31 to the valve-chamber 35. A

sleeve or thimble 4 is slidable on the stem of the valve.

10 and is biased by the spring 33 bearing against the valve-guide '27 towards and against a transverse pin 40 which 'is located in the back-head, so that a substantial clearance is normally maintained between the interior face 9 of the thimble and the end of the valve stem.

In order, therefore, that the valve 10 may be opened by manual operation .of a trigger 5, which is pivotally mounted in the back-head, the thimble 4 must be moved sufliciently far to take up the lost motion due .to the clearance between the end of the stem of the valve 10 and the interior face 9 of the thimble 4.

' In order to provide, in accordance with the invention, for obstruction of the actuation of the valve 10, inthe example shown an external circumferential groove 7, preferably of rectangular cross-section, is provided in the thimble 4, and this groove 7 cooperates with an obstructor in the form of the end of a piston rod 3 attached toa piston 36 that forms part ofmeans respon-. sive to the pressure of the liquid supplied to the liquid inlet 11 of the drill. The piston 36 cooperates with a cylinder constituted by a bush 15 fitted in a bore of the back-head and closed at one end by an apertured plug 37. The piston rod 3 is sealed by a gland in the upper end of the bush 15. A spring 17 is disposed between the plug 37 and the head of the piston 36 and urges the piston upwardly so that the reduced end of the piston rod 3, constituting the obstructor, normally enters the groove 7 and precludes manual actuation of the thimble 4 by means of the trigger 5 to open the valve 10.

The liquid inlet nipple 11 is connected through a slot 12, through an external passage 13 in the back-head, through a groove 14 in the bush 15 and through a port 16 to the space 1 above the head of the piston 36.

As has been mentioned, the thimble 4 is normally locked by engagement of the end of the piston rod 3 with the annular groove 7, and the valve 10 cannot be manually opened. When pressure in the space 1 above the head of the piston 36, that is the pressure of the liquid supplied to the nipple 11, reaches some predetermined value, for which the spring 17 has been set up, for example, fifteen pounds per square inch, the piston 36 and piston rod 3 are retracted and the end of the piston rod is withdrawn from the annular groove 7, so that the valve 10 may be manually opened. 4

The liquid controlling.

In order to control the flow of liquid, a mushroom type valve 6 biased towards a seating 18 by a spring 20 bearing against the nipple 11 is provided, the seating being above the passage 13. The seating 18 is provided upon a bush 38 inserted in a bore of the back-head, and the bush provides a guide for the stem 39 of the valve 6, which projects into the bore of the back-head in which the thimble 4 slides. When the valve 6 is opened the liquid flows into the chamber 21 above the valve 6, through a passage 22 to an annular groove 23, and then through a passage 24, through an annular groove 26 formed in the valve guide 27, through a passage 25 formed in the back-head, through a tube 28 bridging the joint between the back-head and the drill cylinder 30, through the duct 29 to a swirl spray assembly 8 of conventional design mounted near the end of the drill.

A chamfered circumferential groove 19 is formed in the thimble 4, into which groove the end of the valve stem 39 normally projects, this groove 19 providing an external cam surface cooperating with the valve stem 39. When the thimble 4 is moved by manual operation of the trigger and before the lost motion provided by the normal clearance between the face 9 of the thimble 4 and the end of the stem of the valve is taken up, the side of the groove 19 engages cam-wise the end of the valve stem 39 and causes opening of the valve 6 to admit liquid to the spray assembly 8. Thus, liquid is sprayed before compressed air is admitted to the pneumatic motor of the drill.

If the supply of liquid to the nipple 11 is cut ofi during actual operation of the drill, such operation is not automatically stopped by the construction shown and described. However, this is of minor importance, because drilling is normally carried out in short bursts, and, whenever the trigger 5 is released, the thimble 4 will return to its normal position under the action of the spring 33 and, if the liquid supply has failed or is of insufficient pressure, will remain locked in that position by the end of the piston rod 3.

It will be appreciated that one particular manner of applying the invention to a particular form of pneumatic drill has been described with reference to the accompanying drawing by way of example only, and that many modifications may be made without departing from the scope of the invention.

What is claimed is:

1. A pneumatic drill of the kind referred to comprising a retractable obstructor normally so cooperating with the manually operable air valve as to preclude manual opening of the air valve, and comprising means connected with the obstructor and responsive to the pressure of the liquid supplied to the liquid inlet of the drill to retract the obstructor when subjected to not less than a predetermined liquid pressure.

2. A pneumatic drill according to claim 1, comprising a movable obstructor biased by a spring to a position in which it precludes manual opening of the air valve, a piston and cylinder combination connected with the obstructor, the piston and cylinder combination being so arranged and so connected to the liquid inlet of the drill that the pressure of liquid therein acts against and, when it exceeds a predetermined value, overcomes the bias of the spring, thus to retract the obstructor thereby permitting opening of the manually operable air valve.

3. A pneumatic drill according to claim 1 and comprising a liquid-controlling valve, wherein the air valve is biased to its closed position and actuated by amember having a lost motion connection with the valve and so biased that such lost motion must be taken up before opening of the air valve, and wherein a liquid controlling valve is so connected with the member as to be opened thereby during the taking up of the lost motion.

4. A pneumatic drill according to claim 3 wherein the air valve is a mushroom or like rectilinearly actuated valve, having a stem, wherein the actuating member is a sleeve or thimble slidable relative to the stem and biased by a spring to ensure a normal clearance between an abutment on the sleeve or thimble (eg. the closed end of the thimble) and the end of the stem, wherein the sleeve or thimble has an external cam surface cooperating with the liquid controlling valve so as to open it during the taking up of the lost motion.

5. A pneumatic drill according to claim 4 wherein the liquid controlling valve is of the mushroom type having a stem that cooperates with the cam surface of the sleeve or thimble.

References Cited in the file of this patent UNITED STATES PATENTS 2,205,736 Schorle June 25, 1940 2,721,540 Fuehrer Oct. 25, 1955 2,777,424 Fuehrer Ian. 15, 1957 FOREIGN PATENTS 624,190 Great Britain May 30, 1949 633,052 Great Britain Dec. 5, 1949 

